The document discusses the different modes of the 80386 processor: Real Mode which allows direct access to memory and I/O but no protection; Protected Mode which allows features like virtual memory and paging for increased security and multi-tasking by enabling descriptor tables and the PE bit; and Virtual Mode which allows real mode applications to run on protected mode systems by virtualizing memory.

1. Real Mode- Unlimited direct software access to all memory,
I/O address & hardware.
Protected Mode- It allows system software to use features such
as virtual memory, paging and safe multi-tasking designed to
increase an operating system's control over application software.
It begins executing instructions in real mode.
It starts after the system software sets up several descriptor
tables and enables the Protection Enable (PE) bit in the control
register 0 .
 Virtual Mode - Allows the execution of real mode applications
that are incapable of running directly in protected mode
Paging – Organize the available physical memory in to 4kb size
each, under segmented memory.
8/22/2014 Modes of 80386
Modes of 80386

2. 8/22/2014 Modes of 80386